The present invention relates generally to a new and improved construction of an arbor for use with a hole saw. More specifically, the invention relates to a hole saw arbor having a spring biased, quick release drive collar capable of translation between an extended and a retracted position and further capable of independent rotation about a central axis of the arbor when the drive collar is in the retracted position to facilitate alignment of the drive pins on the collar with the drive apertures in the hole saw base, and also to provide a unique means for maintaining the collar in a retracted position while the saw is threaded on the arbor.
Various general constructions of hole saw arbors, and associated quick release drive collars, are well known in the field, as is evidenced by the following patents.
______________________________________ Blanch, et al. 1,645,736 10/18/27 St. Palley 2,674,026 04/06/54 Elsy 2,754,864 07/17/56 Benjamin, et al. 2,727,748 12/20/55 Webster 2,917,975 12/22/59 Morse 3,647,310 03/07/72 Reeves 3,679,220 07/25/72 Segal 3,976,387 08/24/76 Bixler 4,893,426 01/16/90 ______________________________________
The general construction of a hole saw arbor employs a first end constructed so as to be insertably attached to an air or electrically powered tool, such as a drill, which can supply the necessary torque to the hole saw and a second end to which a hole saw and a drill bit, used to drill a pilot hole for the hole saw, are engaged. The hole saw is threadably attached to the second end. This means of attachment, while satisfactory for small diameter hole saws, a singular threaded connection is unacceptable for larger diameter hole saws. More specifically, the larger the diameter of the hole saw, the greater the torque created during cutting. This torque can cause the threads on the saw base and the arbor to be over torqued, resulting in galling and damage to the threads. If this damage occurs it is particularly difficult for a workman to remove the hole saw from the arbor or to re-assemble the saw for later use.
Thus, it was necessary to provide means capable of preventing torque on the hole saw from being transmitted directly to the threads. As disclosed in a number of prior art patents, and more specifically in the patent of Meshulam, U.S. Pat. No. 3,758,221, a plate or collar is provided having a plurality of drive pins or projections. The drive projections are inserted into apertures in the hole saw, and this interconnection accommodates the torque present on the hole saw. However, with this prior art design the drive plate and the hole saw are held on the second end by means of a nut. This construction results in an extended time period necessary to change hole saws.
The patent of Bittern, U.S. Pat. No. 3,784,316, discloses an improvement in hole saw arbors. A threaded drive ring having drive pins, insertable into apertures in the hole saw, is provided on the second end of the hole saw arbor, along with the hole saw, which is also threadably attached to the second end. Specifically, the threads attaching the drive ring to the arbor are oppositely directed to the threads attaching the hole saw to the arbor. For example, if the threads attaching the drive ring are left-handed, then the threads attaching the hole saw are right-handed. Additionally, a locking ring is provided, which is spring biased against the drive ring. This construction also demands an extended time period necessary to change hole saws.
The patents of Clark, et al., U.S. Pat. No. 4.036,560, and Clark, U.S. Pat. No. 4,148,593, disclose even further improvements in the construction of hole saw arbors. Specifically, a drive collar, having projecting pins insertable into apertures in the hole saw, is translatable between an extended and a retracted position along the hole saw arbor. The drive collar is maintained in either of these positions by means of a ball detent device. The hole saw is threaded onto the second end with the drive collar in the retracted position. Thereafter, the detent device is released, and the drive collar translated along the arbor so that the pins are inserted into the hole saw apertures.
The above-disclosed devices provide constructions that reduce the time period necessary for changing hole saws, however, there are still inherent disadvantages. The drive collar is not rotatable about the hole saw arbor. This means that a workman must align the pins on the drive collar with the apertures in the hole saw as he threads the hole saw on the arbor. It is difficult to perform this alignment with the drive collar in the retracted position, which was necessary to thread the hole saw onto the arbor. Also, if the hole saw is provided with but a single set of drive apertures, considerable manipulation is required to attain proper alignment.
The hole saw arbor construction of the present invention provides a quick release means that can reduce the time needed to, and increase the ease of changing hole saws. This new construction facilitates alignment of the drive pins on the drive collar with the apertures in the hole saw. Also, means for holding the drive pins firmly within the apertures are provided, as is means to maintain the collar in the retracted position as the hole saw is threaded on the arbor.